textproduct: Rapid City

KEY MESSAGES

- Mild and breezy on Wednesday with isolated showers and thunderstorms possible.

- Critical fire weather conditions Wednesday over parts of northeastern WY and southwestern SD. Near critical conditions again on Friday.

- Unsettled weather through the weekend per a series of fronts with up/down temperatures trending coolish for the weekend.

UPDATE

Issued at 1029 PM MDT Tue Jun 9 2026

KUDX/KLNX radar shows the line of thunderstorms have pushed east of the CWA border. Have cancelled the Tornado Watch. Surface obs show the cold front has crossed NW SD and portions of NE WY...and is now crossing Sturgis to Bison to Lemmon. Gusts behind the front have been in the 30s/40s mph range. With the trough drifting along the MT/Canadian border, more weak shortwaves will round the base and cross the CWA overnight into Wednesday. Could see some elevated showers/iso storms develop overnight into the Wed morning hours. Highs tomorrow will be much cooler...in the 70s/lower 80s. Cool air aloft and an approaching jet streak will support some shower development Wednesday, but could be mostly limited to NE WY/NW SD. Critical fire weather concerns will return Wednesday, but will be limited to southern Campbell/Weston counties in NE WY through Fall River/Oglala Lakota counties in SW SD. RH will drop below 15% while westerly winds gust up to 45 mph. Have issued a Red Flag Warning earlier in the evening (see Fire Weather Discussion below for more info).

DISCUSSION

(This Evening Through Tuesday) Issued at 1201 PM MDT Tue Jun 9 2026

18z surface analysis had low over southwest ND with a wavy stationary front into MN, a dry-line into the Black Hills, and a cold front into southwest WY. Gusty southeast winds ahead of dry- line per 3-5mb/3hr pressure falls in ND. Morning water vapour loop/0.5km visible imagery showed a distinct MCV moving from central NE to eastern SD early this afternoon. Widening our view, upper trough over the northwest CONUS with embedded jetlet/shortwave over WY heading our way. Effects of these features the main forecast concern.

Latest ensemble guidance indicate shortwave will lift northeast this afternoon with attendant increase in mid-level flow overtopping dryline. 2-3KJ/kg mean MUCAPE per SPC HREF pools ahead of dryline with weakening MLCIN. Preliminary look at 18z KUNR sounding shows the MLCIN well, in an otherwise deeply mixed- sounding with steep lapse rates to 500mb. Effective shear forecast to increase to 35-45kts. Most CAMS suggest convective initiation between 09/19-21z over northwestern SD nearest the dry- line/stationary front interface. Convection should zipper south/south-east through the late afternoon/early evening hours, moving east/northeast. Any discrete storms have the potential for very large hail and isolated tornadoes. Right now, main mode looks to be linear with potential for signficant wind gusts given 1800 DCAPE and CAM wind gust output for the eastern half of the CWA. Best conditions for supercells develop east/north of CWA this evening. Confidence in thunderstorms is high, but how they evolve/strengthen will be dependent on where the boundaries are in relationship to upper forcing given lower confidence to severe weather evolution.

Colder air filters into the area tonight with noticeably cooler weather for Tuesday along with some shra/TS per cyclonic flow/very weak buoyancy.

Rest of the forecast looks unsettled as a series of disturbances traverse the northern plains per northwest flow aloft. Deeper trough brings higher PoPs/cooler temperatures for the weekend. Each front/disturbance will bring gusty winds.

AVIATION

(For the 06Z TAFS Through 06Z Wednesday Night) Issued At 1029 PM MDT Tue Jun 9 2026

VFR conditions are generally expected through the forecast period. Isolated to scattered showers and perhaps thunderstorms are possible overnight tonight into Wednesday. MVFR/IFR conditions and gusty, erratic winds are possible with any heavier storms. A cold front cross the area tonight will bring gusty northwest winds across most locations through Wednesday.

FIRE WEATHER

Issued At 918 PM MDT Tue Jun 9 2026

A cold front will cross the area tonight, bringing breezy northwest winds through Wednesday, along with cooler temperatures. However, there will be an area of very dry air (down to 11 percent) and gusty westerly winds (gusts to 45 mph) across portions of the northeastern Wyoming plains through the southwestern South Dakota plains. This will result in critical fire weather conditions late Wednesday morning through the early evening. A Red Flag Warning has been issued.

The rest of the week will be unsettled as a series of fronts move through, each containing gusty winds and variable temperatures. Elevated to near-critical fire weather conditions are expected Friday due to very dry air (teens minimum relative humidity over northeastern Wyoming and southwestern South Dakota).

UNR WATCHES/WARNINGS/ADVISORIES

SD...Red Flag Warning from 11 AM to 8 PM MDT Wednesday for SDZ322-326. WY...Red Flag Warning from 11 AM to 8 PM MDT Wednesday for WYZ315-317.